Lawn mower tire sizes are printed on the sidewall and typically use one of two formats. The most common small-equipment format lists width and rim diameter, such as 13×5.00-6, where 13 is the overall tire diameter in inches, 5.00 is the section width, and 6 is the rim diameter. Some turf tires use an automotive-style format like 18×8.50-8 or a metric style, but the key is to locate the sidewall markings and match the diameter, width, and rim size when replacing a tire.
Where to Find the Tire Size Markings
Before you can decode a tire size, you need to locate the markings. On most lawn mower tires, the size information is molded into the sidewall, the vertical surface of the tire between the tread and the rim.
Where Are the Size Numbers Printed on a Lawn Mower Tire?
Look on the sidewall of the tire, typically on the outer face that faces away from the mower. The markings are raised or embossed rubber and can be found in a band around the tire. On some tires, the size appears on both sidewalls, while on others it may only be on one side. If you can’t see it on the outside, check the inner sidewall, which may require removing the wheel from the mower.
What Do the Markings Look Like on a Turf or Small-Equipment Tire?
On a turf or small-equipment tire, the size typically appears as a series of numbers separated by an x and a dash, such as 13×5.00-6 or 16×6.50-8. These markings are usually accompanied by the manufacturer’s name, the tire model, and sometimes the maximum load and inflation pressure. The size may be printed in a slightly larger or bolder font than the other markings, making it easier to spot.
How to Decode the Common 13×5.00-6 Format
The most common size format for lawn mower tires uses three numbers that describe the tire’s dimensions in inches. Understanding what each number represents is key to choosing the right replacement.
What Does the First Number in a Lawn Mower Tire Size Represent?
The first number is the overall tire diameter, measured in inches from the top of the tread to the bottom when the tire is mounted and inflated. In the example 13×5.00-6, the 13 means the tire has an overall diameter of 13 inches. This measurement includes the height of the tread above the rim, so it is larger than the rim diameter.
What Do the Width and Rim Diameter Numbers Mean?
The second number, 5.00, is the section width, which is the widest point of the tire measured from sidewall to sidewall when mounted and inflated. The third number, 6, is the rim diameter in inches, which is the size of the wheel that the tire fits onto. So a 13×5.00-6 tire is 13 inches tall, 5 inches wide, and fits a 6-inch rim. These three dimensions together define the tire’s overall size and fitment.
Understanding Automotive-Style and Metric Formats
While the 13×5.00-6 format is most common on lawn mowers, some turf tires use different sizing conventions. Recognizing these formats helps you decode any tire you encounter.
What Does an Automotive-Style Size Like 18×8.50-8 Mean?
An automotive-style size uses the same three-number structure but is often applied to larger turf tires. In 18×8.50-8, the 18 is the overall diameter in inches, 8.50 is the section width, and 8 is the rim diameter. This format is essentially the same as the standard lawn mower format, just with different dimensions. The key difference is that automotive-style tires may use a different tread pattern or load rating, but the size decoding is identical.
How Do Metric Tire Sizes Differ From the Standard Lawn Mower Format?
Metric tire sizes use a different structure, typically expressed as width/aspect ratio-rim diameter, such as 145/70-6. In this format, 145 is the section width in millimeters, 70 is the aspect ratio (the sidewall height as a percentage of the width), and 6 is the rim diameter in inches. Metric sizes are less common on lawn mowers but may appear on some commercial or imported equipment. To convert a metric size to inches, divide the width in millimeters by 25.4, and calculate the sidewall height by multiplying the width by the aspect ratio percentage.
Using the Size to Choose a Replacement Tire
Once you’ve decoded your tire size, you can use it to select a replacement. Matching the correct dimensions ensures the tire fits properly and performs safely.
Which Numbers Must Match When Replacing a Lawn Mower Tire?
At minimum, the rim diameter must match exactly, since the tire must fit onto the existing wheel. The overall diameter and section width should also match closely to maintain the mower’s ground clearance, cutting height, and handling. A tire with a different diameter can change the mower’s speed and deck height, while a different width can affect steering and clearance. For best results, replace the tire with one that matches all three numbers.
Do I Need to Match the Rim Diameter or Just the Overall Tire Size?
The rim diameter is the most critical number, because a tire with the wrong rim size physically cannot fit onto the wheel. The overall diameter and width can vary slightly without making the tire unusable, but matching them keeps the mower’s performance consistent. If you’re unsure, consult your mower’s owner’s manual or the tire manufacturer’s specifications to confirm the correct size.
Common Questions About Lawn Mower Tire Sizes
Many mower owners have questions about sizing beyond the basic decoding. Here are answers to some of the most frequent inquiries.
Can I Use a Wider Tire on the Same Rim?
In some cases, a slightly wider tire can be mounted on the same rim, but this is not always safe. A wider tire may rub against the mower’s frame, fenders, or steering components, and it can alter handling. The rim width limits how wide a tire can safely fit. Check the rim’s width and the tire manufacturer’s recommended rim range before installing a wider tire.
How Do I Measure a Tire If the Markings Are Worn Off?
If the sidewall markings are worn or illegible, you can measure the tire manually. Measure the overall diameter from the top of the tread to the bottom across the center of the tire. Measure the section width at the widest point of the sidewall. To determine the rim diameter, measure the distance across the rim from one bead seat to the opposite bead seat. These measurements give you the three numbers needed to identify a replacement size.
Reading a lawn mower tire size is a simple skill once you understand the format. By locating the sidewall markings and decoding the diameter, width, and rim size, you can confidently choose the correct replacement tire and keep your mower running smoothly.
